Vehicles, such as cars, trucks, or work machines, use a supercharger to enhance efficiency of the engine and to increase engine power. A supercharger is a device that pressurizes the air intake to above atmospheric pressure. By pressurizing air, the supercharger enables a greater mass of oxygen per cycle of the engine to be available for combustion. More specifically, more fuel is needed to produce more power. However, one cannot simply add more fuel into the engine if there is not enough oxygen to burn the fuel. By providing more oxygen to the system, the supercharger makes adding more fuel to the system possible. Since more fuel is available to be burned and more work can be done per cycle, the power produced by the engine is increased. Supercharging may add more horsepower and more torque to a driveline of the vehicle.
To provide more power to the vehicle, however, the efficiency of the supercharger needs to be at its peak. The supercharger outlet air may be recirculated back through the inlet of the supercharger to reduce the pressure and input power the engine receives during conditions where maximum supercharger power is not required. This circular bypass, however, results in wasted capacity and returns heated air to the inlet of the supercharger, thus reducing supercharger efficiency. In this case, for a supercharger to work at peak efficiency, the heated, compressed air exiting the supercharger must be cooled before it enters a combustion chamber of the engine.
In addition, the exhaust gas emitted from the engine goes through a catalyst, such as a catalytic converter, before being emitted out of the vehicle. The catalyst functions to convert the toxic byproducts of combustion in the exhaust to less toxic substances through chemical reactions. The temperature at which exhaust catalysts usually operate is around 150-600° C., though some catalysts can function at higher temperatures. Although many catalysts are designed to withstand prolonged high-temperature operation and repeated exposure to temperatures in excess of 800° C., a high temperature may pose a number of serious effects. High temperature may affect all the components of the catalysts. For example, the noble metal particles may sinter, resulting in a decrease in the fraction of the metal available for catalytic reactions.
One way to lower the temperature of exhaust gas going into the catalyst is to inject fuel into the exhaust stream. However, this would result in an increase in fuel use and a decrease in fuel economy.
Therefore, an improved system to maximize the efficiency of the supercharger as well as to cool the exhaust gases going into the catalyst is needed.